Multiple thermally-responsive overload relay unit



Sept. 14, 1954 H. E. SCHLEICHER 2,689,287

MULTIPLE THERMALLY-RESPONSIVE OVERLOAD RELAY UNIT Filed March 20, 1953Patented Sept. 14, 1954 MULTIPLE THERMALLY-RESPONSIVE OVERLOAD RELAY UNIT Harold E. Schleicher, West Hartford, Conn., as-

signor to The Arrow-Hart & HegemanElectric Company, Hartford, Conn., acorporation of Connecticut Application March 20, 1953, Serial No.343,552

This invention relates to thermally-responsive relay switching devices;and more particularly to overload relays for a plurality of linesemploying interchangeable heater elements in the different lines whichinfluence identical bimetallic elements that may be separately adjustedand that act upon a single releasing member, individually orcooperatively.

An object of this invention is to provide a device of theabove-mentioned type as an integral unit which can be connectible in thepower lines and used as a component of electro-magnetic switchingapparatus of either remote or adjacent control.

Another object is to provide a device of the aforesaid type wherein asingle contact is released which acts also as the sole means to latchitself and the releasing member in tripped position.

Another object is to provide a device having theaforesaidcharacteristics which is of simple unitary construction, having aminimum number of parts and which can be economically manufactured andassembled.

Another object is to provide a device having the aforesaid advantagesand characteristics which nevertheless will be accurate in operation andof rugged construction to stand heavy overloads through the heaterelements without deleterious effect on its operation.

Another object is to provide a device as aforesaid in which the thermalgenerating parts of the several lines are interchangeable from the frontand are also interchangeable for like parts of different rating, andwhich are nevertheless isolated from each other mechanically andelectrically.

Another-object is to provide a device of the aforesaid type havingmanually resetting means readily available from the front of the device.

Other objects and advantages of the invention will become apparent asthe invention is described in connection with the accompanying drawing.

In the drawing:

Fig. 1 is a plan view of a device embodying the invention.

Fig. 2 is a bottom view of the device of Fig. 1.

Fig. 3 is a transverse section view taken along line 3--3 of Fig. 1.

Fig. 4 is a perspective view of the rocker element used in the device ofFigs. 1-3. V

Fig. 5 is a perspective view of the bimetallic element and shield usedin the device of Figs. 1-3.

Fig. 6 is a perspective view of the manual reset button used in thedevice of Figs. 1-3.

12 Claims. (Cl. 200-116) Referring to the drawing, the parts are mountedin a molded insulating base In whichhas molded into its upper surfacethree parallel elongated cavities Illa, lob and "1c running from one endto the other of the base. The walls of the cavities serve to isolateeach bimetal from its neighbor. Similar bimetallic strips 20 are mountedin the bottom of each cavity, one end of each strip being secured to amounting bracket 22 which in turn is secured to the base by bolts. Themounting bracket 22 may be stamped from sheet metal into oblique angularshape as indicated in the Fig. 5 and may be provided with an adjustmentscrew 24 threaded into one leg. The end of the screwis adapted to pressagainst one end of a small flat oblique-angled pivoted lever 23 set intoa slot in the side of the base in such way that the other end of thelever is pressed against the underside of the bimetal strip 20 near thepoint of its securement to the mounting bracket 22. By tightening up orloosening the adjustment screw 24, the free end of the bimetal 20 iscaused to move slightly and in that way its position may be adjusted.

At opposite ends of each cavity Hm, I [lb and H10 are located stampedsheet metal wire terminal members Ha, Ha, I2b, Mb etc. for connection tothe power lines. Connected with one terminal located above the bimetal20 in each cavity is a metallic plate [8 provided to shield the bimetalfrom a heater coil I1. Each coil may be located in a ceramic hood orhousing It above the plate [8 in its own cavity. The heater coil and itshousing are of usual construction and are connected across the terminalsH11 and Ma, I22; and Nb, etc. The bimetallic elements 20 are preferablymade identical so as to be mountable recessed to receive a rockerelement 3!! of irregular form as illustrated best in Fig. 4. Preferablythis rocker element 30 will be molded from insulating material and willbe mounted upon a pivot pin 3| passing lengthwise through the rockerelement and having its ends seated in 3 bearing recesses [r molded intothe bottom base of the insulating base Ill.

The rocker element is provided with three spaced fingers 33a, 33b and330 respectively extending laterally thereof in position to be engagedby the ends of the free bimetallic elements 20. The rocker element isnormally biased in the direction opposite to the pressure exerted by thebimetallic elements when they bend.

Referring to Fig. 3, the right end of the bi metallic elements will benddownwardly when heated. This causes the rocker elements to pivot in acounterclockwise direction. tension spring 38 provides a bias for therockor element 30 by having one end engaged with a spring anchor lug 32molded upon the rocker element while the other end of the spring isanchored to a metal pin 39 molded into the insulating base and extendingfrom the bottom face thereof;

The rocker elementis designed to cooperate with and cause operation ofaspring contact strip 0' which may be stamped from resilient conductivethin sheet metal. One end ofsaid resilient contact strip 40- (the leftendin Fig. 211' is between the bottom of the base ill and a stampedsheet metal terminal bar 44 by a screw bolt 45 which passes through theendof the terminal and the end of the spring contact 40. A contactbutton 42- of good contact such as silver is mounted upon the springcontact 40 near its free end in position to engage acombined contact andterminal member 46 stamped from sheet metal L-sh-ape and secured to thebottom of the base ii by screw boltsc spring contact-40- is providedwith a nor-- mal inherent bias away from the fixed content and terminalmember 48-. In order tohold the spring. contact in engagement with thefined contact 48,. there isprovided upon the rocker member 30 ii-lateral extension designated gen erally by 34 and acts as holdingelement or latch. The latch- '34 is preferably molded" upon the rocker3minthe form illustrated in Fig.4 with aheadportiomfli ataxia-shoulderadjacent there tohavinga top surface and a side surface 31. the:bimetallic members are cool and the movable contactstrip 40 has itsbutton 4! in engagement with the fixed contact 46, the end at theoontaotstrip will lie flat upon title surface 36 of the latch member 34a Theside of the head 35 on the latch: member. prevents the spring. 88 frompulling the rocker member tar in clockwise direction (referring to Fig.3%.. This clockwise rotation is also halted: by the engagement of thefingers 33d, 33b and 3h their respective bimetallic elements.

The terminals We and 14a; W2) and Nb etc. are=oonnecuibie in the powerlines of an electriccircuit to'engage the coils H separately in each.line. The heat generated in each: coil by an overload current thus thebimetals with it. Upon the occurrence of an overloadin any one oi the'threerlines'comn-ciled by, the device, or in all-three, the-coil W inthe affected line or lines will up; The: heat will) be tmnsmitted thrwghplate" 18 to the bimetallic element 20: Upon heating, thebl metallicelement will: have its right and (referring. to Fig. 3) bend downwardlypressing against one-"or anotheror fire-imam "a; 88!) or 33c. Uponenentwith tite f'mgca.

the rocker -30: will be caused to pivot iri coufiter .A coiied clockwisedirection whereupon the surface 38 of the latch element 34 will moveaway from the end of the spring contact 40. Thereupon the spring contactdue to its normal bias and resiliency will move away tram thefixedcontact IG breaking ihe circult controlled by thbse confacts. (Seedotted position of Fig. 3). This circuit ordinarily will be a control orsignal circuit not carrying full load current.

"is prevented from returning to its previous position, despite coolingof the bimetala by the engagement of the end of the movable contactstrip 40 with the side surface 31 of the latch extension 34. Thisengagement prevents the biasing spring 38 from reversely moving therocker 30. Hence the contact strip "40 not only functions as a movablecontact but also as a latch in these circumstances.

In order to reset the device after the bimetallic elements have cooled,there is provided a manual reset button 56 which preferably is moldedfrom insulating material in form as illustrated in Fig.6. The button hasan upper portion which extends thrcugha passage molded through thebasefrom the top to the bottom surface. with the top end of the button ingabove the top of the to be available from the front or top of the base.its bottom or inner end abuts the inner surface of the contact strip(0". Hence by pressing on button the contact 40 is moved toward and iscaused to engage 'fi'xed contact-4t. At-thesame time the end of' thestrip 46 moves over the side surface- 31 of the shoulder on the latchextension 34' until it reaches the top surface 38 otthe shoulder.Thereupon under theurge 0t spring 38' the rocker 3a snaps in clockwisedirection (Fig. 33'. Thereafter the surface 36 holde-the contactsengaged as before.

In tripped pocition,- i e. the positionv (dotted in" Fig 3) after therocker has caused to move by heating. of the bimetallic elements thespring contact 40 pressing. against the lower or inner end of the manualreset button causes that button to move upwardly. To limit the upwardmovement, the button 50 is provided at its mid-portion: with lateralenlargements formingshouldersil After the fixed-andmovqable contactshave separated; the shoulders I engage with ashoulder (not visible)withinthe Passage through which. the buttonpanel. In this way, the resetbattomis kept fromm ingout of the base in an wawamd directiom-' It islikewise limited in its downward movement by engagement with-- theccntactwr From the foregoing, it will be observed that it one or anotherofthe bimetale under the effect of the/heat generated lathe heater mile11,. the rocker element is caused to pivotband permit the-fixed andmovable contact sweeperate; andtheyare held apart-by the rocker men Iteven; atter the binetale-cook After metals have cooled, the manual resetbuttcnemdy be depressed to cause the fixed and-mcwable obnto; engageagain. .At the same? time; the spring will cause the rocker 30 to -M lnclockwise direction (Flea 2 8811 3) caueing'ithe surface to overlie-theendot the movaiblecbntact 40, thus holding the contactr dofid when themanueL-reset button-"ls" released.

Thus, I havepmviuec wmpisrem er umt liremally l espflfime miafis'fliichunit-18 adapted to be asse tions iir' amj anciepuw simmer-circuits areuiilt connected to electmmag'fletw switching apparatus. The sevice iscompact and similar parts in adjacent cavities are alike formanufacturing economy. Moreover, the heater coils may be interchangedwith like parts of different current ratings, so that they may not onlybe interchanged from one cavity to another but may also be exchanged fordifferently rated coils. Thus, the heaters may be of the same ordifferent rating in different lines to accommodate the unit to allvariations of possible use. Further the device is made mainly fromstamped parts which may be readily manufactured with a maximum ofeconomy and may be assembled with ease. Moreover, the foregoingadvantages are all achieved while reserving maximum accuracy with ruggedconstruction. Since the current-carrying parts of the main lines areinsulated physically and electrically from the current-carrying parts ofthe contacts of the auxiliary or control circuit 40 and 46, burnoutdamage to the heater coils from a short circuit in the main power linesmay be accomplished without affecting their replacement and function ofthe device.

Although the contacts 40 and 46 are illustrated as being normallyclosed, it will be obvious to those skilled in the art that it is withinthe scope of the invention to apply it to normally open contacts whichWould become latched closed upon the heating of the bimetallic elements.

Many modifications within the scope of the invention will occur to thoseskilled in the art. Therefore I do not limit the invention to thespecific form of the embodiment illustrated and described.

What I claim is:

1. An electric relay switch comprising an insulating base, a pluralityof thermally responsive elements in parallel arrangement on one side ofsaid base in cavities, means on said base isolating each element fromits neighbor, fixed and movable contacts on the opposite side of saidbase, a rockable member pivotally mounted on said opposite side of {saidbase and engaging with one of said contacts to hold it in one position,said rockable member being moved by one or more of said thermallyresponsive elements to release said contact when one or more of saidelements are heated.

2. An electric relay switch comprising an insulating base, a pluralityof thermally responsive elements on one side of said base, relativelymovable contacts on the other side of said base normally biased into oneposition, a rockable member pivotally mounted on said other side of saidbase and movable in position to maintain one of said contacts inposition against said bias, said rockable member being rockable by saidthermally responsive members to release said contact, and means on saidrockable member to maintain said contact in another position regardlessof the condition of said thermally responsive members thereafter.

3. An electric relay switch comprising an insulating base, a pluralityof thermally responsive elements on one side of said base, relativelymovable contacts on the other side of said base, a rockable memberhaving latching means thereon, means pivotally mounting said rockablemember on said other side of said base, said rockable member beingmovable in position to latch one of said contacts in position againtssaid bias, said rockable member being rockable by said thermallyresponsive members to release said contact and latch it in anotherposition regardless of the condition of said thermally responsivemembers thereafter.

4. An electric relay as claimed in claim 2 having manually operableresetting means to cause said rockable member to move into saidpositionagainst-said-bias.

5. An electric relay as claimed in claim 4 wherein the resetting meanscomprises a member passing through the base and accessible from saidfirst-mentioned side of the base.

6. An electric switch as claimed in claim 3 having a manually operableresetting means to cause said rockable member to move in position tolatch said one contact in said position-against-saidbias.

'7. An electric switch as claimed in claim 6 wherein the resetting meanscomprises a member passing through the base and accessible from saidfirst-mentioned side of the base.

8. An electric relay switch comprising an insulating base, a pluralityof thermally responsive elements on one side of said base, relativelymovable contacts on the other side of said base, a rockable memberpivotally mounted on said other side of the base and rockable to latchsaid contacts in one position, means biasing said rockable member towardsaid latching position, said thermally-responsive members when heatedmoving said rockable member from latching position, and one of saidcontacts engaging said rockable member after said movement from latchingposition to prevent said biasing means from retuming said rockablemember to latching position.

9. An electric relay switch as claimed in claim v8 having manualresetting means extending through said base for said rockable member andcontacts and accessible from the front.

10. An electric relay as claimed in claim 9 wherein the thermallyresponsive elements are separately connectible in different lines of anelectric power line and the contacts are connectible in a controlcircuit, said base being formed to provide a shield between adjacentthermally responsive elements and between them and the contacts.

11. A compact electric relay unit as claimed in claim 8 wherein thethermally responsive elements are arranged in isolated parallelrelation, and said base being formed to provide barriers betweenadjacent elements and a barrier between them and the contacts on theopposite side, and a resetting button for said contacts passing throughsaid base between two adjacent thermal elements.

12. An electric relay switch as claimed in claim 8 having individualadjustment means for the individual thermal elements to move the ends ofsaid thermal elements relatively to said rockable member, saidadjustment means being available from the front of the base, and manualresetting means extending through said base for said rockable member andcontacts and accessible from the front.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,108,812 Fisher et al. Feb. 22, 1938 2,286,965 Johnson June16, 1942 2,418,537 Wood Apr. 8, 1947

